1. Field of the Invention
The present invention relates to an ophthalmic insert and method for the release of medication to the eye for the treatment of eye disorders. More specifically, the present invention relates to punctal plugs sized to pass through a lacrimal punctum and be positioned within a lacrimal canaliculus of the eyelid and containing medication for controlled release into the eye.
2. Discussion of the Related Art
Active agents frequently are administered to the eye for the treatment of ocular diseases and disorders. Conventional means for delivering active agents to the eye involve topical application to the surface of the eye. The eye is uniquely suited to topical administration because, when properly constituted, topically applied active agents can penetrate through the cornea and rise to therapeutic concentration levels inside the eye. Active agents for ocular diseases and disorders may be administered orally or by injection, but such administration routes are disadvantageous in that, in oral administration, the active agent may reach the eye in too low a concentration to have the desired pharmacological effect and their use is complicated by significant, systemic side effects and injections pose the risk of infection.
The majority of ocular active agents are currently delivered topically using eye drops which, though effective for some applications, are inefficient. When a drop of liquid is added to the eye, it overfills the conjunctival sac, the pocket between the eye and the lids, causing a substantial portion of the drop to be lost due to overflow of the lid margin onto the cheek. In addition, a substantial portion of the drop that remains on the ocular surface is drained into the lacrimal puncta, diluting the concentration of the drug.
To compound the problems described above, patients often do not use their eye drops as prescribed. Often, this poor compliance is due to an initial stinging or burning sensation caused by the eye drop. Certainly, instilling eye drops in one's own eye can be difficult, in part because of the normal reflex to protect the eye. Therefore, sometimes one or more drops miss the eye. Older patients may have additional problems instilling drops due to arthritis, unsteadiness, and decreased vision, and pediatric and psychiatric patient populations pose difficulties as well.
It is known to use devices that may be inserted into one or more of an orifice of an individual's eye, such as a lacrimal punctum, to deliver active agents. One disadvantage of using such devices to deliver agents is that much of the agent may delivered in an initial, large bolus upon insertion of the device into the eye rather than a more linear delivery of the agent over time.
Prior topical sustained release systems include gradual release formulations, either in solution or ointment form, which are applied to the eye in the same manner as eye drops but less frequently. Such formulations are disclosed, for example, in U.S. Pat. No. 3,826,258 issued to Abraham and U.S. Pat. No. 4,923,699 issued to Kaufman. Due to their method of application, however, these formulations result in many of the same problems detailed above for conventional eye drops. In the case of ointment preparations, additional problems are encountered such as a blurring effect on vision and the discomfort of the sticky sensation caused by the thick ointment base.
Alternately, sustained release systems have been configured to be placed into the conjunctival cul-de-sac, between the lower lid and the eye. Such units typically contain a core drug-containing reservoir surrounded by a hydrophobic copolymer membrane which controls the diffusion of the drug. Examples of such devices are disclosed in U.S. Pat. No. 3,618,604 issued to Ness, U.S. Pat. No. 3,626,940 issued to Zaffaroni, U.S. Pat. No. 3,845,770 issued to Theeuwes et al., U.S. Pat. No. 3,962,414 issued to Michaels, U.S. Pat. No. 3,993,071 issued to Higuchi et al., and U.S. Pat. No. 4,014,335 issued to Arnold. However, due to their positioning, the units are uncomfortable and poor patient acceptance is again encountered.